Process for coating surfaces with polyepoxide compositions



United States Patent Claims. (31. 117-622) 10 ABSTRACT OF THE DISCLOSUREA process for coating surfaces is disclosed. This process comprisesspreading a liquid coating containing a polyepoxide and a polymercaptanon the surface and then applying an accelerator for the epoxy/mercaptanreaction. This process also comprises applying an accelerator for anepoxy/mercaptan reaction to a surface, and then spraying on top thereofa mixture of a polyepoxide and a polymercaptan.

This application is a continuation of the application Ser. No. 289,428,filed June 20, 1963, and now abandoned.

This invention relates to a process for curing polyepoxides. Moreparticularly, the invention relates to a new process for curingpolyepoxides at a fast rate using polymercaptan curing agents withaccelerators.

Specifically, the invention provides a new and efiicient process forcuring at a fast rate at low temperatures polyepoxide-polymercaptanmixtures which have a good pot life or storage stability at these sametemperatures. The process comprises applying in separate applications(1) a polyepoxide-polymercaptan mixture, and (2) an accelerator for theepoxy-mercaptan reaction, such as, a tertiary amine by, for example,spraying the accelerator onto a layer of the polyepoxide-polymercaptan.

Polyepoxides, such as, for example, those obtained by reactingepichlorohydrin with polyhydric phenols in the presence of caustic, arepromising materials for use in many industrial applications as they canbe reacted with curing agents to form insoluble infusible productshaving good chemical resistance. The conventional polyepoxidecuringagent systems, however, have certain drawbacks that have limited theiruse for certain applications. For example, the known systems takeconsiderable time to cure at low temperatures. With the best aliphatictype amine curing agents, the systems take several hours to set to ahard product, Because of this, it has been difficult to use thepolyepoxide systems for applications, such as highway coatings,maintenance surface coatings and the like, where the coating must dry ina very short time. 55

It has been found that polymercaptans accelerated with materials, suchas tertiary amines, can be used to cure the polyepoxides at a rapid rateat low temperatures. Here, however, the problem has been of too rapid acure time. Once the components have been combined together, the mixturebegins to set up and there is little pot life or storage time for thecomposition. This necessitates mixing just before the use and as aresult there are diiiiculties in large scale operations such as coatingof highways. etc.

It is, therefore, an object of the invention to provide a new processfor curing polyepoxides. It is a further object to provide a new processfor curing polyepoxides that brings about a fast cure at lowtemperatures. it is a further object to provide a new process for rapidcure of polyp epoxides which involves the use of compositions having along pot life. it is a further object to provide a new technique whichprovides a long working time with the polyepoxide coating compositionbut which brings about a rapid cure at low temperatures. It is a furtherobject to provide a new process for preparing polyepoxide coatings. Itis a further object to provide a new process for preparing polyepoxidecoatings which have improved physical properties. These and otherobjects of the invention will be apparent from the following detaileddescription thereof.

It has now been discovered that these and other objects may beaccomplished by the new process of the invention which comprisesapplying in separate applications (1) a polyepoxide-polymercaptanmixture, and (2) an accelerator for the epoxy-mercaptan reaction, suchas, for example, a tertiary amine. As a preferred embodiment, theprocess involves applying a fluid medium containing thepolyepoxide-polymercaptan mixture and then applying over the topthereof, such as spraying a layer of a solution containing theaccelerator. It has been found that by the above technique, one canutilize solutions with extremely long pot life which can be premixed andallowed to stand for long periods of time. Yet when the two solutionsare brought together by the above technique, the combination rapidlysets up at low temperatures to form the desired hard insoluble infusibleproduct.

That one could obtain the above results was quite unexpected as it wasthought heretofore that it was necessary to etiect a thorough mixing ofthe accelerator with the epoxy-polymercaptan mixture before the desiredcure could be obtained. It was surprising to find that this was notnecessary. All that appears necessary is that some contact be madebetween the accelerator and the epoxypolymercaptan mixture and that theresulting mixture then rapidly sets up throughout to form the desiredproduct.

According to the process of the invention, one of the solutions to beemployed comprises a mixture of the polyepoxide and the polymercaptan.The polyepoxides to be used comprise those materials possessing morethan one vicinal epoxy group, i.e., more than one group. These compoundsmay be saturated or unsaturated, aliphatic, cycloaliphatic, aromatic orheterocyclic and may be substituted with substituents, such as chlorine,hydroxyl groups, ether radicals and the like. They may be monomeric orpolymeric.

For clarity, many of the polyepoxides and particularly those of thepolymeric type are described in terms of epoxy equivalent values. Themeaning of this expression is described in US. 2,633,458. Thepolyepoxides used in the present process are those having an epoxyequivalency greater than 1.0.

Various examples of polyepoxides that may be used in the process of theinvention are given in US. 2,633,458 and it is to be understood that somuch of the disclosure of that patent relative to examples ofpolyepoxides is incorporated by reference into this specification.

Other examples include the epoxidized esters of the polyethylenicallyunsaturated monocarboxylic acids, such as epoxidized linseed, soybean,perilla, oiticia, tung, Walnut and dehydrated castor oil, methyllinoleate, butyl linoleate, ethyl 9,12-octadecadienoate, butyl9,12,15-octadecatrienoate, butyl eleostearate, monoglycerides of tungoil fatty acids, monoglycerides of soybean oil, sunflower, rapeseed,hempseed, sardine, cottonseed oil and the like.

Another group of the epoxy-containing materials used in the process ofthe invention include the epoxidized esters of unsaturated monohydricalcohols and polycarboxylic acids, such as, for example,

Another group of the epoxy-containing materials includes thoseepoxidized esters of unsaturated alcohols and unsaturated carboxylicacids, such as 2,3-epoxybutyl 3,4-epoxypentanoate,

3,4-epoxyhexyl 3,4-epoxyhexyl 3,4-epoxypentanoate,

3,4-epoxycyclohexyl 3,4-epoxycyclohexanoate,

3,4-epoxycyclohexyl 4,5-epoxyoctanoate,

2,3-epoxycyclohexylmethy epoxycyclohexane carboxylate.

Still another group of the epoxy-containing materials includedepoxidized derivatives of polyethylenically unsaturated polycarboxylicacids such as, for example,

dimethyl 8,9,12,l3-diepoxyeicosanedioate,

dibutyl 7,8,l1,l2-diepoxyoctadecanedioate,

dioctyl 10,1l-diethyl-8,9,12,13-diepoxy-eicosanedioate,

dihexyl 6,7,10, l l-diepoxyhexadecanedioate,

dodecyl 9-epoxy-ethyl-10,1l-epoxyoctadecanedioate,

dibutyl 3-butyl-3,4,5,6-diepoxycyclohexane-1,2-

dicarboxylate,

dicyclohexyl 3,4,5,6-diepoxycyclohexane-l,2-

dicarboxylate,

dibenzyl 1,2,4,S-diepoxycyclohexane-1,2-

dicarboxylate and diethyl 5,6,l0,1l-diepoxyoctadecyl succinate.

Still another group comprises the epoxidized polyesters obtained byreacting an unsaturated polyhydric alcohol and/or unsaturatedpolycarboxylic acid or anhydride groups, such as, for example, thepolyester obtained by reacting 8,9,12,l3-eicosanediene-dioic acid withethylene glycol, the polyester obtained by reacting diethylene glycol,with 2-cyclohexene-1,4-dicarboxylic acid and the like, and mixturesthereof.

Still another group comprises the epoxidized polyethylenicallyunsaturated hydrocarbons, such as epoxidized 2,2-bis(2-cyclohexenyl)propane, epoxidized vinyl cyclohexene and epoxidized dimer ofcyclopentadiene.

Another group comprises the epoxidized polymers and copolyrners ofdiolefins, such as butadiene. Examples'of this include, among others,butadiene-acrylonitrile copolymers (Hycar rubbers), butadiene-styrenecopolyrners and the like.

Another group comprises the glycidyl containing nitrogen compounds, suchas diglycidyl aniline and diand triglycidylamine.

The polyepoxides that are particularly preferred for use in thecompositions of the invention are the glycidyl ethers and particularlythe glycidyl ethers of polyhydric phenols and polyhydric alcohols. Theglycidyl ethers of polyhydric phenols are obtained by reactingepichlorohydrin with the desired polyhydric phenols in the presence ofalkali. Polyether A and Polyether B described in the above-noted US.2,633,458 are good examples of polyepoxides of this type. Other examplesinclude the polyglycidyl ether of 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane (epoxy value of 0.45 eq./ 100 g. and melting point C.),polyglycidyl ether of 1,l,5,5-tetrakis(hydroxyphenyl)pentane (epoxyvalue of 0.514 eq./ g.) and the like and mixtures thereof.

The polymercaptans employed in the above compositions comprise thosehaving a plurality of free SH groups. The number of mercapto groups willvary depending chiefly on the nature of the polyepoxide. Thus, thepolyepoxides which have approximately two epoxy groups are preferablyreacted With polymercaptans having more than 2 and preferably 3 to 6 SHgroups. The polyepoxides which have more than about two epoxy groups arepreferably reacted with polymercaptans having approximately 2 -SHgroups. The nature of the polymercaptan itself may vary depending on thenature of the product desired, i.e., fluid or solid, odor, toxicity andthe like. In general, the polymercaptans may be aliphatic,cycloaliphatic or aromatic or heterocyclic and may be substituted withother substitutents, such as OH groups, halogen atoms, ether and esterradicals and the like. They may also be monomeric or polymeric.

Examples of polymercaptans include mercapto-substituted hydrocarbons,ester, ethers, urethanes, sulfides and the like, such as glyceroltrithioglycolate, pentaerythritol tetrathioglycolate, 1,2,6-hexanetrioltrithioglycolate, glycerol trithiolacetate, 1,2,6 hexanetrioltrithiolacetate, 1,2,4-butanetriol tri(2-mercaptobutyrate),tri(mercaptobutyl) ether of glycerol, tetra(mercaptoethyl) ether ofpentaerythritol, di(mercaptoethyl) ether of 1,4-butanediol, tributylether of 1,4,6-trimercapto-2,5,8-octanetriol, esters ofmercapto-substituted alcohols and polycarboxylic acids, such astri(mercaptobutyl) pyromellitate, tri(mercaptobutyl)1,2,4butanetricarboxylate, trimercaptoethyl) trimellitate,tri(mercaptohexyl) 1,3,5-pentanetricarboxylate and mercaptoethyl estersof polyacrylic acid, mercaptobutyl esters of copolyrners of methacrylicacid and styrene, 2,4,S-trimercaptotoluene-l,6-diisocyanate,1,4-di(mercaptomethyl) 2,3,5,6-tetramethylbenzene, trimercaptophenol,bis(2,4-dimercaptobutyl) sulfide, bis (3,5-dimercaptohexyl) sulfide,bis(2,4-dimercaptobutyl-) sulfone and the like, and mixtures thereof.

Other highly functional polymercaptans that can be used include thoseobtained by reacting polyepoxides with hydrogen sulfide. Examples ofthese are set out in US. 2,63 3,458. A special group of these includethose obtained by reacting polyepoxides having more than 2 epoxy groupswith hydrogen sulfide. Examples of such polyepoxides include, amongothers, glycidyl ethers of polyhydric alcohols containing at least threeOH groups, such as glycerol, 1,2,6-hexanetriol, pentaerythritol,polyvinyl alcohol, polyallyl alcohol, 1,3,5-pentanetriol, polyolsobtained by reacting trihydric or higher alcohols with dibasic acids,polyols obtained by hydration of polyepoxides containing two or moreepoxy groups, polyols obtained by homopolymerizing and copolyrnerizingvinyl or allylic monomers containing OH groups, such as hydroxyethylacrylate and the like.

Other examples of polyepoxides possessing more than 2 epoxy groupsinclude the glycidyl ethers of polyhydric phenols containing at leastthree OH groups, such as, for example, 1,3,5-trihydroxybenzene,2,2-bis(4,6-dihydroxyphenyl)propane, 2,2 bis(4,6dihydroxyphenyl)sulfone, and l,3,5-trihydroxynaphthalene, and polyhydricphenols obtained by reacting phenols with formaldehyde (novolac resins),the glycidyl ethers of which are represented by the formula Anothergroup of polyepoxides possessing more than 2 epoxy groups to be reactedwith the hydrogen sulfide include, among others, those esters of epoxyalcohols and polycarboxylic acids containing at least three carboxylgroups, and alternatively, those esters of epoxy acids and polyhydricalcohols or phenols containing at least three OH groups. Examples ofsuch esters include, among others, triglycidyl ester of1,2,4-butanetricarboxylic acid, triglycidyl ester of1,3,6-hexanetricarboxylic acid, triglycidyl ester of trimellitic acid,glycidyl ester of poly(acrylic acid), glycidylesters of poly(methacrylicacid), glycidyl ester of pyromellitic acid, and ester of2,3-epoxypropionic acid and 1,2,6-hexanetriol, ester of2,3-epoxypropionic acid and glycerol, esters of 3,4-epoxybutanoic acidand polyvinyl alcohol and the like.

The highly functional mercaptan products are obtained by reacting theabove-noted polyepoxides with hydrogen sulfide. The amount of thehydrogen sulfide to be employed may vary, but it is preferred to use anexcess of the hydrogen sulfide. For best results it is preferred to addthe polyepoxide and hydrogen sulfide in mol ratios of 1:20 to 1:4, andmore preferably from 1:10 to 1:3. The reaction between the polyepoxideand hydrogen sulfide is preferably accomplished in the presence ofcatalysts, such as alkaline materials as sodium hydrosulfide, sodiumethoxide, sodium phenoxide and the like, and small amount of aminecompounds, such as diethyl amine, melamine and the like. The amount ofcatalyst employed may vary from about .001% to about 5% by weight. Thetemperature employed in the reaction may vary over a wide range. In someinstances, it may proceed at low temperatures such as -l5 C., to roomtemperatures. Preferred temperatures range from about C. to 100 C. Atthe completion of the reaction, the polymercaptan can be recovered byany suitable means, such as distillation, extraction, filtration and thelike.

Illustration of the above method for making highly functionalpolymercaptans is given below for the reaction of a glycidyl ether of anovolac resin with hydrogen sulfide:

About 500 parts of a glycidyl polyether of novolac resin having an epoxyvalue of 2.82 eq./100 g. was dissolved in toluene. Hydrogen sulfide wasbubbled into the reaction mixture until the mixture was saturated. Themixture was allowed to stand overnight and then distilled to yield aviscous liquid polymercaptan having a -SH value of .41 eq./l00 g.

Other examples of polymercaptans include those obtained by reactingpolythiiranes with hydrogen sulfide as disclosed and claimed incopending patent application Ser. No. 231,852, filed Oct. 19, 1962 nowUS. Patent No. 3,369,040, issued Feb. 13, 1968, and so much of thatdisclosure pertinent to the preparation of these polymercaptans isincorporated herein by reference.

Other polymercaptans include those obtained by adding hydrogen sulfideto polyunsaturated compounds, such as polybutadienes, polyisoprenes andthe like, This addition is preferably accomplished in the presence ofcatalysts, such as isopropylamine. 'Ilhese mercaptan substitutedpolymers preferably have molecular weights varying from about 150 toabout 10,000 as determined ebullioscopically in toluene.

Another group of special polymercaptans include the mercapto-substitutedheterocyclic compounds, such as tri(mercaptomethyl) trioxanes, and thelike, as described and claimed in copending application Ser. No.254,365, filed May 31, 1963; now issued US. Patent No. 3,297,635, andaromatic compounds substituted with mercapto-containing side chains,such as described and claimed in copending application Ser. No. 284,322,filed May 31, 1963; now issued US. Patent No. 3,310,527, and so much ofthese disclosures pertinent to the preparation of these newpolymercaptans is incorporated herein by reference.

Especially preferred polymercaptans to be employed in the process of theinvention include the esters of the polyhydric alcohols andmercapto-substituted mono and polycarboxylic acids, the esters of themercapto-substituted alcohols and the polycarboxylic acids, the adductsof hydrogen sulfide and polyepoxides, the adducts of hydrogen sulfideand polythiiranes, the mercapto-substituted heterocyclic compounds andthe aromatic compound su-bstituted With mercapto-substituted sidechains. These special polymercaptans preferably contain no more than 25carbon atoms.

The accelerators for the reaction of the above-described polyepoxidesand polymercaptans include, among others, the phenols, sulfides,tertiary amines, organic phosphines, organic arsines, or-ganic antimonycompounds, amine salts, or quaternary ammonium salts, and the like.Preferred activators are the phenols, phosphines, arsines, amines, andsulfides, such as, for example benzyldimethylamine dicyandiamidep,p'-bis(dimethylaminophenyl) methane, pyridine, dimethyl aniline,dimethylethanolamine, methyldiethanolamine, norpholine,dirnethylarninopropylamine, dibutylaminopropylamine,stearyldimethylamine, tri-n-butyl amine, N,N-dibutyl butylamine,tri-nhexylamine, ethyl di-n-propylamine, phenylene diamine, diethlenetriamine, dibutyl sulfide, dioctyl sulfide, dicyclohexyl sulfide and thelike, and mixtures thereof. The salts may be exemplified by theinorganic and organic acid salts of the amines, such as, for example,the hydrochloride, sulfate and acetate of each of the above-describedtertiary amines. The quaternary ammonium salts may be exemplified by thefollowing: benzyltrimethylammonium chloride, phenyltributylammoniumchloride, cyclohexyltributylammonium sulfate, benzyltrimethylammoniumsulfate, benzyltrimethylammonium borate, diphenyldioctylammoniumchloride, and the like, and mixtures thereof.

Particularly preferred activators to be used are the sulfides,phosphines and tertiary amines, and more preferably the monoand diamineswherein the amine hydro gens have been replaced by aliphatic,cycloaliphatic, or aromatic hydrocarbon radicals containing not morethan 15 car-hon atoms, such as, for example, the trialkyl amines,triaryl amines, triarylalkylamines, alkyl arylalkyamines,tricycloalkylamines, alkyl dicycloalkylamines, diaminoalkanes,dialkylene triamines, phenylene diamines and di(aminoaryl) alkanes.Preferred amine salts are the hydrochloride, sulfate and acetate of theabove-described preferred amines. The preferred quaternary salts arethose of the formula wherein Y is nitrogen, R is an alkyl, aryl orarylalkyl radial, preferably containing no more than 12 carbon atoms andX is chlorine.

In the operation of the process of the invention, one mixture isprepared containing the polyepoxide and the polymercaptan and the secondcomponent is the accelerator. The mixture containing the polyepoxide andthe polymercaptan can be prepared by merely mixing the two componentstogether. The ratio of the two components may vary over a wide range. Ingeneral, the polyepoxide is combined with at least .8 equivalent of thepolymercaptan. As used herein equivalent amount refers to that amountneeded to furnish one SH group per epoxy group to be reacted. Preferablythe polyepoxide and polymercaptans are combined in chemical equivalentratios varying from about 1.5:8 to .8:1.5.

The mixture of polyepoxide and polymercaptan is preferably employed in amobile condition. If the component or components are thick liquids orsolids, this may be accomplished by heating the mixture or by use ofdiluents or solvents. Various solvents or diluents may be employed.These may be volatile solvents which escape from the polyepoxidecompositions containing the adduct by evaporation before or during thecuring such as, esters such as ethyl acetate, butyl acetate, Collosolveacetate (ethylene glycol monoacetate), methyl Cellosolve acetate(acetate ethylene glycol monomethyl ether), etc., ether alcohols, suchas methyl, ethyl or butyl ether or ethylene glycol or diethylene glycol;chlorinated hydrocarbons such as trichloropropane, chloroform, etc. Tosave expense, these active solvents may be used in admixture witharomatic hydrocarbons such as benzene, toluene, xylene, etc., and/ oralcohols such as ethyl, isopropyl or n-butyl alcohol. Solvents whichremain in the cured compositions may also be used, such as diethylphthalate, dibutyl phthalate and the like, as Well as cyano-substitutedhydrocarbons, such as acetonitrile, propionitrile, adiponitrile,benzonitrile, and the like. It is also convenient to employ apolyepoxide, such as one of the glycidyl polyethers of the dihydricphenol, in admixture with a normally liquid glycidyl polyether of apolyhydric alcohol. In fact, two or more of any of the polyepoxides maybe used together as mixtures. In such a case, the amount of the adductadded and commingled is based on the average epoxide equivalent weightof the polyepoxide mixture.

The accelerator component may be applied as such or in solvent ordiluent. As only small amount of the accelerator is actually needed forthe operation, it is generally preferred to add the accelerator in theform of a solution. Suitable solvents or diluents include those utilizedabove for the other mixture containing the polyepoxide andpolymercaptan.

The amount of the accelerator to be utilized in the final curing processmay vary over a wide range. As the reaction is a catalyst reaction, theamount is not critical. In general, it is preferred to utilize about .1%to by weight of the polyepoxide. This type of proportion is generallyobtained by the use of solutions in the range of from 1% to 80% inconcentration. If one applies the accelerator solution by spraying, itis preferred to utilize the solutions having concentrations varying fromabout 5% to about 50%, and more preferably from about to Various othercomponents can be mixed with the solution containing the polyepoxide andpolymercaptan or the solution containing the accelerator. Examples ofsuch materials include, among others, pigments, fillers, dyes,extenders, such as tars, asphalts, resins, plasticizers and the like.

According to the process of the invention, the cure is accomplished byapplying the above-noted two solutions in separate applications. Thus,the solution containing the accelerator may be first applied and thesolution containing the polyepoxide and polymercaptan can then beapplied over the top of the first, or alternatively, the solutioncontaining the polyepoxide and polymercaptan can be applied first andthen the solution containing the accelerator. Further, the inventioncontemplates the simultaneous application of the two solutions such asby applying the two solutions simultaneously from two separate sprayguns onto the surface to be coated. Thus, the time elapsing betweenapplications is not important as long as the solutions are introducedfrom separate containers or sources of supply and mixed at the site ofuse, e.g., as on the surface to be coated.

As noted. above, the polyepoxides can be cured according to the processof the invention at the low reaction temperature, e.g., ambienttemperature, so there is no need to apply external heat. However, insome cases, it may be desirable to apply some heat to increase the rateof cure. Suitable temperatures preferably range from about 15 C. toabout 150 C., with the more preferred range varying from about 15 C. to75 C. With small castings, it is preferred to cure at room temperatureand then post cure for a few hours at elevated temperatures, say from C.to 150 C. For surface coatings, it is generally preferred to effect thecure at the lower range of temperatures from 15 C. to about 50 C. Thecure time will vary from a few minutes to a few hours depending on thetype and quantity of reactants, thickness of film, etc. Clear relativelythin surface coatings generally cure in a matter of 5 to 20 minutes.

As noted above, one of the great advantages of the present process isthe long pot lives of the two solutions as well as the rapid cure whenneeded. As shown in the working examples, the mixture of polyepoxide andp-olymercaptan have pot lives of several days, but when used in theprocess are able to be cured in a matter of minutes.

The above process may be utilized in many important commercialapplications. The process is particularly suited for use in preparingsurface coatings, and particularly those requiring rapid cures as fornon-skid highway coatings, coating of loading areas, storage areas,factory floors, storage tanks and the like, as well as many conventionalapplications, such as painting of ships, automobile parts, etc. In theseapplications, the two solutions are prepared as above and any of thespecial techniques are employed in applying the two solutions.

The above process is also applicable in lamination and filament windingapplications. In this latter application, the filaments, such as, forexample, glass fibers are passed into and through one of the liquidcompositions and then wound onto the desired mandrel or form. The secondsolution can be applied to the glass roving before, during or after theapplication of the other solution. The finally treated composition canthen be cured in conventional manner. One advantage of the presentprocess is that the composition can be cured at low temperatures andthis would thus not affect any heat sensitive material that may bepresent. For example, the rubber lining of missile cases are heatsensitive and would be affected by the use of high temperatures forcuring material thereon, The new process thus could be used for filamentwinding of these cases where the winding is directly on the liner.

The new process is also applicable in other uses, such as in theformation of adhesives, in the formation of thin coats of electricalapparatus as in encapsulation applications and the like.

To illustrate the manner in which the invention may be carried out, thefollowing examples are given. It is to be understood, however, that theexamples are for the purpose of illustration and that the invention isnot to be regarded as limited to any of the specific conditions orreactants recited therein. Unless otherwise specified parts described inthe examples are parts by weight. The polyethers referred to by letterhereinafter are those set out in U.S. 2,633,458.

Example I This example illustratesthe preparation of a fast drying clearcoating using Polyether A containing butyl glycidyl ether, a hydrogensulfide adduct of a phenolformaldehyde resin and benzyl dimethtylamineas the accelerator.

parts of Polyether A containing 15 parts of butyl glycidyl ether wascombined with 156 parts of an adduct of hydrogen sulfide and aphenol-formaldehyde resin having a mercaptan value of .41 eq./ 100 g.and 156 parts of a solvent made up of equal parts xylene, methylisobutyl ketone, and Cellosolve. This mixture was spread on tin panelsto form a coating of about 3 mils thick. A catalyst solution containing50 parts of benzyl dimethylamine and 200 parts of solvent made up ofequal parts of xylene, methyl isobutyl ketone and Cellosolve wasprepared and sprayed onto the layer of Polyether A and polymercaptanalready applied to the tin panels. The mixture was then allowed to sethard at room temperature. The product dried hard in 5 to 10 minutes toform a hard insoluble infusible coating. The pot life of the PolyetherA-polymercaptan solution was over 3 days.

A similar coating was prepared by premixing the benzyl dimethyl aminewith the Polyether A and hydrogen sulfide adduct before the mixture wasapplied as a coating. In this case the coating set up in 30 minutes. Thepot life of the solution, however, was only 30 minutes also.

A glycidyl polyether of polyepichlorohydrin having a formula asdescribed in US. 3,058,921, having a molecular weight of 615 and anepoxy value of 0.388 eq./100 g. was used as a replacement for /2 and forof the Polyether A. Related results were obtained with each of thesesystems.

A glycidyl polyether of polyepichl-orohydrin was used as a replacementfor of the Polyether A. Related results were again obtained.

A similar coating was also prepared by applying only the Polyether A andhydrogen sulfide adduct. In this case, the coating dried in about 17hours and the pot life was about 3 days.

A review of the drying times and pot lives of the above coatings isgiven below:

Catalyst Dry Hard Pot Life 3 days. 30 minutes. 3 days.

Example II Titanium calcium pigment 450 Diatomacious silica 35 Calciumcarbonate 75 This mixture was spread on tin panels to form a coating ofabout 15 mils thick. A catalyst solution containing 50 parts ofbenzyldimethylamine and 200 parts of a solvent made up of equal parts ofxylene, methyl isobutyl ketone and Cellosolve was prepared and sprayedonto the layer of Polyether A and polymercaptan applied as above. Themixture was then allowed to set hard at room temperature. The productdried hard (tack free) in 5 to minutes and dried through in less than 17hours. The product had a pot life of greater than 2 days.

A similar coating prepared without the use of the catalyst dried hard(tack free) in 60 minutes with through dry of hours.

Example III Example II was repeated using tris(mercaptoethyl) trioxanein place of the hydrogen sulfide adduct. Related results are obtained.

the accelerator employed is diethyl sulfide. Related results areobtained.

Example VI Examples I and II are repeated with the exception that thesolution containing the benzoldimethylamine is applied to the tin platefirst and then the solution containing Polyether A and hydrogen sulfideadduct spread over the top as by spray application. Related results areobtained.

Example VII Examples I and II are repeated with the exception that thetwo separate solutions were sprayed simultaneously from spray gunsplaced close together over the tin plate. Related results are obtained.

Example VIII Examples I to IV are repeated with the exception that thePolyether A is replaced with Polyether B and Polyether C. Relatedresults are obtained.

Example IX Examples I and II are repeated with the exception that theaccelerator employed is as follows: triphenyl phosphine, tricyclohexylphosphine and triamyl phosphine. Related results are obtained in eachcase.

Example X Examples I and II are repeated with the exception that thepolymercaptan employed is as follows: 1,2,6-hexanetrioltrithioglycolate, pentaerythritol tetrathioglycolate, hydrogen sulfideadduct of diglycidyl ether of 2,2-bis(4- hydroxyphenyl) propane, 1-dimercaptoethyl) -2,3-dimercaptocyclohexane, and the tri(mercaptoethyl)ether of glycerol. Related results are obtained.

Example XI Examples 1, II, VI, VII and X are repeated with the exceptionthat the accelerator employed is as follows: ben- Zyltrimethylammoniumchloride, phenyltributylammonium chloride and benzyltrimethylammoniumborate. Related results are obtained in each case.

We claim as our invention:

1. A process for producing a coating of a cured polyepoxide compositionon a surface at a fast rate at a temperature below about C. whichconsists of spreading out on the surface a film of a liquid coatingcontaining as the only reactive components a polyepoxide having morethan one vie-epoxy group and at least 0.8 equivalent of a polymercaptancontaining more than two --SH groups, then applying on the top of thatfilm a coating containing as the only reactive component an acceleratorfor the epoxy-mercaptan reaction, and allowing the combined compositionto set hard at a temeprature below 50 C.

2. A process as in claim 1 wherein the polyepoxide is a liquid glycidylpolyether of a polyhydric phenol.

3. A process as in claim 1 wherein the polymercaptan is a hydrogensulfide adduct of a glycidyl ether of a phenol-aldehyde condensate.

4. A process as in claim 1 wherein the accelerator is a tertiary amine.

5. A process as in claim 1 wherein the accelerator is a dialkyl sulfide.

6. A process as in claim 1 wherein the solution containing theaccelerator is applied by spraying.

7. A process as in claim 1 wherein the accelerator is a quaternaryammonium salt.

8. A process as in claim 1 wherein the accelerator is a phosphine.

9. A process as in claim 1 wherein the polymercaptan is a hydrogensulfide adduct of a polythiirane.

10. A process for coating a surface with a cured polyepoxide compositionat a fast rate at a temperature below 50 C. which consists of applying afilm of a liquid coat ing containing as the only reactive component anaccelerator for an epoxy-mercaptan reaction to the desired surface,spraying on top of the film a coating containing as the only reactivecomponents a mixture of a polyepoxide having more than one vie-epoxygroup and at least 0.8 equivalent of a polymercaptan, and allowing theresulting combined composition to set hard at a temperature of 150 C. to50 C.

References Cited UNITED STATES PATENTS Shokal 117-132 X Mika 117-161 XSaewert et a1. 117-622 X Ingrassia 117-161 X Dowling 117-161 X 12Patterson et a1. 117-161 X Winchester 117-622 X Varlet 117-622 Proops260-831 X Newey et a1. 260-47 Bergman et a1. 260-47 De Acetis et a1260-47 Mendoyanis 260-830 10 WILLIAM D. MARTIN, Primary Examiner.

M. LUSIGNAN, Assistant Examiner.

